Strange generic compilation behaviour - also javac/eclipse difference

Question

Hello!
With my friends I've stumbled upon a problem in understanding how the compiler (and Java Language Specification too) treats a specific generic declaration.
public class Main {
    public static void main(String args[]) {
        ArrayList<Integer> inParam2 = new ArrayList<Integer>();
        List<Number> returnValue2 = justDoIt(inParam2);
    public static <E extends Number> List<E> justDoIt(List<? super E> nums) {
        return null;
}The code compiles fine with javac and throws compile error in eclipse. The latter, I believe, is the proper behaviour - what am I missing? The method justDoIt could be possibly resolved in two ways:
public static List<Number> justDoIt(List<Number> nums)or
public static List<Integer> justDoIt(List<Integer> nums)both will give reasonable and well-documented compile time errors. The first is because ArrayList<Integer> can't be passed to List<Number> (and even more - Integer is not a supertype of Number, therefore <? super Number> should fail). The latter is because List<Integer> value can't be assigned to List<Number> na main() for obvious reasons. I suppose from these two the compiler would resolve the mentioned static function as the one with Number throughout the declaration... but what really happens? How come the code compiles?
I would be very grateful for any insights.
Best regards,
Mateusz

Answer 1

maticomp wrote:
The code compiles fine with javac and throws compile error in eclipse. Same here. Not even as much as a warning from javac with Xlint:all. Curious.
I would be very grateful for any insights.&#42;cough&#42; I believe the relevant JLS section is this one: [15.12.2.7|http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#341287]. I'll readily admit I felt a bit too flabby today to read all of it.